Conventional fuel system architectures for internal combustion engines sometimes employ a common rail system, which typically requires highly pressurized fuel to be provided to fuel injectors. Such common rail systems often include a low-pressure fuel circuit that provides fuel flow to a high-pressure fuel pump and a high-pressure fuel circuit, which includes the fuel rail and feeds the injectors. In some cases, fuel in the low-pressure fuel circuit is pressurized above atmospheric pressure, 5-6 bar for example, and then the high-pressure fuel pump further pressurizes the fuel to an appropriate high fuel pressure that may be two to three orders of magnitude higher than the low-side fuel pressure (above 1600 bar in heavy duty systems for example) in the fuel rail to facilitate efficient and effective fuel injection for combustion.
Various components facilitate the delivery of low-pressure fuel to the inlet of the high-pressure fuel pump. A combination of a fuel priming pump and a crank driven mechanical gear pump in the low-pressure circuit is utilized in some conventional fuel systems to create the required level of fuel pressure at the inlet of the high-pressure pump. Some systems utilize an electronically controlled fuel transfer pump (eFTP) on low-pressure fuel circuits as an option. However, such conventional fuel system and eFTP systems have not been demonstrated for effective and robust operation.
Various components facilitate the regulation of pressure in the fuel rail. A fuel control valve is often utilized in conventional fuel systems to modulate the fuel flow to the high-pressure pump. In some such systems, the fuel control valve opens or closes in response to pressure in the fuel rail, measured by a pressure sensor, in order to regulate the fuel rail pressure toward an appropriate high fuel pressure. Further, in some systems, a mechanical, pressure-responsive valve (e.g., a pressure-regulating valve or a pressure-relief valve) allows excess fuel pressure above the appropriate pressure to bleed off fuel back to the fuel tank by opening when the pressure exceeds a threshold pressure and/or by regulating pressure toward an appropriate value.
Common failures in such conventional fuel systems include failure of the fuel control valve, failure of the pressure sensor, and/or failure of the pressure-responsive valve. The failure of one or more of these components often results in at least a partial loss of the ability to regulate the fuel rail pressure and thus the effectiveness of injection. Losing the ability to regulate can have undesirable consequences: greater emissions of in-cylinder particulate matter or nitrous oxides (NOX), reduced fuel efficiency (e.g., increase fuel consumption), and/or reduced service life of fuel system components (e.g., accelerated wear and tear damage).
Some conventional fuel systems are designed to substantially, or even severely, derate the engine in response to such failures (e.g., artificially limit torque or power output), with the purpose of mitigating the undesirable effects of the failure. However, derating the engine compromises the engine's performance and often causes noticeable problems for users—such as in on-road applications, wherein an engine fails with the nearest service center being hundreds of miles away, and in off-road applications, wherein an engine failure causes undesirable downtime or unacceptable performance until serviced.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.